As semiconductor technology progresses, microelectronic devices are being fabricated by ever-shrinking dimensions. This development dictates the necessity to employ accurate and reliable metrology, which becomes an increasingly complex and important task. Complementing measurement channels and modeling techniques, allowing the required improvements in measurement capabilities, are essential for the continual process of this development.
Commonly, Optical Critical Dimension (OCD) metrology plays an important role in semiconductor manufacturing process control, due to its unique advantages: it is sensitive, accurate, flexible and relatively fast. OCD metrology is applied to acquire highly accurate and precise information on the geometry and material properties of these structures.
In OCD, measured data including optical scattering information is collected, and analyzed/interpreted using theoretical model(s). The data analysis includes modification of the geometrical and material properties in the modeled structure until a combination of the parameters is found which corresponds to a good agreement between the theoretical (calculated) and measured data. It is then assumed that the model parameters (dimensions, thicknesses, material optical properties etc.), which were found to provide good agreement (best fit) with the measurement, represent the parameters of the measured structure.